Well?

So sometimes I personally like to save mail in case I need to use it again,but at the same time I like to keep my mailbox clean so I know where it is, not to mention to also keep contribution team related stuff in a separate area. That got me thinking, why cant we have sub-categories that we can add on? Like a button on the side that said "add new category" and it sends it to a different tab that you can pull up later on. In all honesty Im not much of a code person but Im sure someone might be able to figure it out?